This invention relates to an apparatus for use in the growth of magnetic garnets by liquid phase epitaxy and in particular to a new and improved substrate holder for use in the dipping apparatus for growing magnetic garnet films on a substrate.
LPE growth of magnetic garnets for bubble domain devices utilizing a dipping technique whereby a substrate is immersed in a crucible of supersaturated solutions is old and well known. The technique described in a number of publications, such as, "Diminishing Transient Growth Effects of LPE Bubble Domain Films" by Davies et al, IBM Technical Disclosure Bulletin, Vol. 17, No. 6, November 1974, page 1841, describing a method of minimizing the effects of a transient layer for films for supporting bubbles smaller than 5 microns; "Liquid Phase Epitaxial Growth of Magnetic Garnet Films by Isothermal Dipping in a Horizontal Plane with Axial Rotation" by Giess et al, Journal of Crystal Growth, Vol. 16, No. 1, October 1972, pp. 36-42, showing a substrate (wafer) holder for mounting a wafer in a horizontal plane for dipping into a crucible; and "The Growth of Magnetic Garnets by Liquid Phase Epitaxy" by Blank et al, Journal of Crystal Growth, Vol. 17, pp. 302-311, 1972 and U.S. Pat. No. 4,092,208 to Brice et al, showing a substrate holder for mounting a substrate vertically for dipping into a melt.
The prior art apparatus employs a substrate holder having a fixed mode of operation, that is, the substrate is held in a horizontal position, in a vertical position, or in a fixed tilted position; the latter facilitating flux runoff from the substrate as it is being removed from the melt.
It is also known that, for film thickness uniformity, the horizontal orientation of the substrate in the melt is most desirable, and, that for good flux runoff, a tilt of the substrate as it is being withdrawn from the melt, is desirable.
Accordingly, it is an object of this invention to provide a substrate holder for liquid phase epitaxy which allows a substrate to have a freedom of movement so that it will orient itself in a horizontal plane during the film growth, i.e., while immersed in a melt, to assure optimum uniformity of film thickness, and so that the substrate will assume a tilted position to provide good flux runoff upon withdrawal from the melt.
It is also known that with a substrate tilt of less than 10.degree. from horizontal, flux runoff is not satisfactory but that a substrate tilt of about 15.degree. from horizontal provides a good opportunity for the flux to runoff.
Thus, a more specific object of this invention is to provide a substrate holder which allows a substrate to have freedom of movement so it will orient itself in a horizontal plane during the film growth process and so that the substrate will assume a tilt of approximately 15.degree. for maximizing flux runoff as a substrate is being removed from the flux.